plant pathogen
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...
ic virus in the family ''
Bromoviridae
''Bromoviridae'' is a family of viruses. Plants serve as natural hosts. There are six genera in the family.
Taxonomy
The following genera are assigned to the family:
* ''Alfamovirus''
* ''Anulavirus''
* ''Bromovirus''
* ''Cucumovirus''
* ''Ilar ...
''. This virus has a worldwide distribution and a very wide host range, having the reputation of the widest host range of any known plant virus. It can be transmitted from plant to plant both mechanically by sap and by aphids in a stylet-borne fashion. It can also be transmitted in seeds and by the parasitic weeds, ''Cuscuta sp.'' (
dodder
''Cuscuta'' (), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the ...
).
Hosts and symptoms
This virus was first characterized in
cucumbers
Cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the Cucurbitaceae family that bears usually cylindrical fruits, which are used as culinary vegetables. beans, carrots, celery, lettuce, spinach, beets, many
ornamentals
Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that i ...
and bedding plants, such as ''
Narcissus
Narcissus may refer to:
Biology
* ''Narcissus'' (plant), a genus containing daffodils and others
People
* Narcissus (mythology), Greek mythological character
* Narcissus (wrestler) (2nd century), assassin of the Roman emperor Commodus
* Tiberiu ...
'', and various weeds. Its presence has been confirmed on every continent of the world, including
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
.
Symptoms seen with this virus include leaf mosaic or mottling (Fig. 1), yellowing, ringspots, stunting, and leaf, flower and fruit distortion. CMV also induces a type of symptom on leaves known as the "shoestring" effect on many host species. This effect causes young leaves to appear narrow and the entire plant to be stunted.
Specifically, CMV can cause cucumbers to turn pale and bumpy. The leaves of these plants turn mosaic and their rugosity is often changed, making leaves wrinkled and misshapen. Growth of these plants is usually also stunted and produces few flowers. Often, cucumber fruits are oddly shaped, appear gray, and tested bitter. These appearances lead to them being referred to as "white pickles".
Tomato
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...
plants are usually stunted and have poorly shaped leaves, or "fernleaf", when infected by CMV. Also certain strains of CMV can cause partial or total crop loss. CMV in
peppers
Pepper or peppers may refer to:
Food and spice
* Piperaceae or the pepper family, a large family of flowering plant
** Black pepper
* ''Capsicum'' or pepper, a genus of flowering plants in the nightshade family Solanaceae
** Bell pepper
** Chili ...
causes slightly different symptoms than the previously mentioned. Pepper plants often have severe foliar damage, shown as mosaic and necrotic rings. Often the peppers themselves are misshapen and contain chlorotic rings and spots. In
celery
Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, ...
, CMV causes streaking and spotting and can be often confused with symptoms of the
celery mosaic virus
Celery mosaic virus (CeMV) is a plant pathogenic virus in the genus'' Potyvirus '' and the virus family '' Potyviridae ''.
In California, mosaic diseases of celery (''Apium graveolens'') were reported as early as 1922. After some time, it beca ...
. Symptoms of CMV in
lettuce
Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae. It is most often grown as a leaf vegetable, but sometimes for its stem and seeds. Lettuce is most often used for salads, although it is also seen in other kinds of food, ...
, such as chlorosis, plant stunting and often do not properly head, can be very similar to those of
lettuce mosaic virus
''Lettuce mosaic virus'' (LMV) is a typical potyvirus (genus ''Potyvirus'', family ''Potyviridae''), which causes one of the major virus diseases of lettuce crops worldwide.
LMV is seed-borne at a low but significant rate (1-10% of the seeds ...
.
CMV has also been identified in a lesser extent to a number of plant species. It is found to be a minor virus infecting
Allium
''Allium'' is a genus of monocotyledonous flowering plants that includes hundreds of species, including the cultivated onion, garlic, scallion, shallot, leek, and chives. The generic name ''Allium'' is the Latin word for garlic,Gledhill, D ...
crops. The virus infection causes extensive malformation on
garlic
Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus '' Allium''. Its close relatives include the onion, shallot, leek, chive, Welsh onion and Chinese onion. It is native to South Asia, Central Asia and northeas ...
plants, and mild malformation to severe necrotic streaks on
onion
An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus '' Allium''. The shallot is a botanical variety of the on ...
leaves. The severe damages on garlic plants and difficulty of aphids transmission of garlic isolate, were possible causal for the rare CMV on garlic. Genetically, the two onion isolates from
Turkey
Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula ...
(CMV-14.3Po and CMV-15.5Po) are highly similar to others isolated from various plant species in Mediterranean, European, and East Asian countries. CMV was also detected on American beautyberry, an important wildlife and pollinator food source plant native to North America.
In plant tissue this virus makes characteristic viral
inclusion bodies
Inclusion bodies are aggregates of specific types of protein found in neurons, a number of tissue cells including red blood cells, bacteria, viruses, and plants. Inclusion bodies of aggregations of multiple proteins are also found in muscle cells ...
which can be diagnostic. They are hexagonal in shape (Fig. 2) and stain both in a protein stain and a nucleic acid stain. The inclusions can also be rhomboidal, may appear hollow (Fig. 2) and can form larger aggregates. The inclusions are not uniformly distributed and can be found in epidermal (Fig. 2), mesophyll, and stomatal cells. These inclusions are made up of virus particles.
Image:CMVCd.jpg, Fig. 1 Symptoms in ''
Commelina diffusa
''Commelina diffusa'', sometimes known as the climbing dayflower or spreading dayflower, is a pantropical herbaceous plant in the dayflower family. It has been introduced to the southeastern United States where it is most common in wet disturbed ...
CMV is non-persistently non-circulatively transmitted by more than 80 different
aphid
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
species, among other vectors. As consequences, the virus is easily spread, and can be found worldwide. CMV infects over 1200 plant species, including important crops and ornamental species. In its plant host, CMV can induce severe damage, which often lead to economical losses, as it has been proven to cause to 10-20% loss of field yield.
Disease cycle
CMV is mainly transmitted by aphids, but it can also be mechanically spread by humans in some cases. However, the mechanically spreading of this virus is not as common as the case of other virus (such as
Tobacco Mosaic Virus
''Tobacco mosaic virus'' (TMV) is a positive-sense single-stranded RNA virus species in the genus ''Tobamovirus'' that infects a wide range of plants, especially tobacco and other members of the family Solanaceae. The infection causes characteri ...
, TMV), because CMV is not a very stable virus. When it is transmitted by aphids, this virus has an acquisition period of five to ten seconds and an inoculation period of about a minute. Nevertheless, after two minutes, the probability of inoculation largely decreases, and within two hours it is practically impossible to transmit it. Moreover, CMV can overwinter in perennial plants and weeds, as it can survive the winter in the roots of the plant and move to the aerial parts in spring, where it can be transmitted by aphids to other plants.
Once the virus penetrates into the host cell, it releases its RNAs into the host cytoplasm. Then, proteins 1a and 2a are produced to enable the virus replication, which takes place i viral factories which are subcellular compartments which increase the efficiency of this process. There, a dsRNA genome is synthetized from the ssRNA(+) and transcribed in order to obtain viral mRNAs as well as new ssRNAs. Afterwards, the capsid proteins are produced and the new viral particles are assembled. Finally, the virus is ready to move to a new cell by triggering the formation of tubular structures which mediate the movement of the virion The short-distance (cell-to-cell) movement of the virus is achieved via plasmodesmata, while the long-distance one (within the plant) occurs via the phloem.
Properties
Genome
CMV is a linear positive-sense, tripartite single-stranded RNA viru Its genome size is 8.623 kb and it is divided among RNA1 (3357 bp), RNA2 (3050 bp), and RNA3 (2216 bp), all of which has a tRNA-like structur These three RNAs encode five proteins, proteins 1a, 2a, 2b, movement protein (MP) and coat protein (CP). While proteins 1a and 2a are responsible for the replication of the virus, protein 2b is the host-silencing suppressor. The RNA is surrounded by a protein coat consisting of 32 copies of a single structural protein which form isometric particles.
Virion
This virus presents non-enveloped, icosahedral or bacilliform virions of 26-35 nm in diameter. The different RNAs are encapsidated in distinct particles, which results in a variety of virion
Environment
CMV is naturally found in temperate areas, where aphids, one of its main vectors, are also found.
Diagnosis
The presence of this virus in a plant can be confirmed serologically (
ELISA
The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presen ...
Currently there is no chemical capable of removing this virus from an infected plant, and therefore the best control is through prevention of the infection and eradication.Pest Alert Cucumber mosaic virus /ref> To achieve this, it is crucial to remove weeds and diseased plants from the field, as well as use clean and sanitized tools. Other options are the use of resistant varieties, or planting so-called " trap crops".
References
Bibliography
*
Other on-line Links about CMV for growers and gardeners
# Texas Plant Disease Handbook Cucumber Mosaic # Weekend Gardener # Ohio Floriculture